Simulation studies of biomagnetic computed tomography (current flow identification)

Simulation studies were performed on phantom models of electrical sources. As a first step toward the development of an imaging algorithm, the simplified problem of identifying the shape and direction of current flow in a planar surface was addressed. The problem was formulated by identifying a space in which the image was to be reconstructed. The space was segmented into a grid. Each grid space represented a current element. The magnetic field at a sampling point due to the current elements was computed using the Biot-Savart law. Since there were many more current elements than sample points, the problem was underdetermined and had an uncountable number of solutions. The projection theorem was used to define an analytic solution for the magnitude and orientation of the current elements in the grid space. The accuracy of the resulting image was determined by comparing it with the known location of the sources shows that shape of the filamentary current flow can be imaged with this technique. The resolution of images based on the sampling of the field, number of voxels in the reconstruction space, and noise is also analyzed.